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Sunflower-Inspired Pattern Increases Concentrated Solar Efficiency

Wednesday, 11 January 2012

There are only a handful of concentrated solar power (CSP) plants in the world. The technology could potentially generate enough renewable energy to power the entire U.S., provided that land and sunlight are in ample supply. Researchers have now come up with a design that reduces the amount of land required to build a CSP plant, while increasing the amount of sunlight its mirrors collect.

A sprawling site called PS10 is a CSP plant in Seville, Spain. Over 600 mirrors, each the size of half a tennis court, track the sun throughout the day, concentrating its rays on the central tower, where the sun’s heat is converted to electricity — enough to power 6,000 homes.

Researchers at MIT and RWTH Aachen University in Germany found that by rearranging the mirrors, or heliostats, in a pattern similar to the spirals on the face of a sunflower, they could reduce the pattern’s “footprint” by 20 percent and increase its potential energy generation. The sunflower-inspired pattern allows for a more compact layout, and minimizes heliostat shading and blocking by neighboring mirrors.

The team consisted of Alexander Mitsos and Corey Noone of MIT and Manuel Torrilhon of RWTH Aachen. Mitsos’ lab developed a computational model to evaluate the efficiency of heliostat layouts. The model divides each mirror into discrete sections and calculates the amount of light each section reflects at any given moment. Noone and Mitsos then ran the dimensions of the mirrors from the PS10 plant through the model, determining the plant’s overall efficiency. The group found that the CSP plant experiences a significant amount of shading and blocking each day despite the staggered layout of its mirrors.

The researchers devised a spiral field with its heliostats rearranged to resemble a sunflower, with each mirror angled about 137 degrees relative to its neighbor. Mitsos says arranging a CSP plant in such a spiral pattern could reduce the amount of land and the number of heliostats required to generate an equivalent amount of energy, which could result in significant cost savings. “Concentrated solar thermal energy needs huge areas,” Mitsos says. “If we’re talking about going to 100 percent or even 10 percent renewables, we will need huge areas, so we better use them efficiently.”

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